There is a new app named Saera being developed to provide a voice controlled experience similar to Siri for the Iphone.
For this app to be fully useful to people who need hands free voice interaction with their device the answer button needs to work outside of answering/ending phone calls with both the wired headset and more importantly the Bluetooth headsets much as it does on phones with voice dialing. Most of the work appears to have been done for wired headsets with these packages:
*Headset Button Enabler - enables wired headset to be used outside calls
*Headset Control - uses wired headset to control Media Player

These apps are designed for pausing and starting the media player but need to be accessable to Python which Saera is written in, and more importantly also need to include the more common bluetooth headsets which does not appaer to be the case.

Saera is one of the killer apps car drivers, cyclists, and motorcycle drivers have waited for on Maemo/Meego.

the Saera thread is here http://talk.maemo.org/showthread.php?t=84753